In the construction industry, it is often necessary to insert piles into and withdraw piles from the earth. A common scenario is the removal of wooden piles and the replacement of these wooden piles with concrete piles.
To insert piles into and remove piles from the earth, a large driving or pulling force must be applied to the pile. Often, vibratory devices are employed to introduce a vibratory force along the axis of the pile during the process of driving or pulling the pile. The combination of a static pulling or driving force with a vibratory or dynamic force is usually sufficient to overcome the earth's resistance and allow the pile to be inserted or withdrawn.
In cases where the pile is being withdrawn from the earth and/or a vibratory force is being applied, a clamping assembly must be provided to allow a pulling force and/or vibratory forces to be effectively transmitted to the pile. Such clamping devices have heretofore comprised a housing that is attached to a vibratory hammer which in turn is suspended from a crane line and/or vibratory device, a first gripping surface securely attached to the housing, a second gripping surface rigidly connected to a pivot arm that is rotatably attached to the housing, and a piston actuator that acts on the pivot arm to force the second gripping surface against the first gripping surface.
Accordingly, to connect a pile to a vibratory device or tensioning cable, the piston actuator is retracted to create a gap between the first and second gripping surfaces. The pile is then inserted between the first and second gripping surfaces and the piston actuator extended such that the pile is gripped between the first and second gripping surfaces. The pile is thus fixed relative to the housing, and the housing itself can be attached to the vibratory device or tensioning cable.
Users have experienced a variety of problems with such prior art clamping assemblies. For example, because piles, especially wooden piles, are often of irregular shapes and sizes, the gripping surfaces do not engage certain of these piles in a manner that effectively transmits tensioning or vibratory loads thereto. This allows the pile to slip within the clamping assembly. This is especially true when the piles are coated with barnacles or other materials that reduce friction between the gripping surfaces and the pile.
Slippage of the pile relative to the clamping assembly lessens the effectiveness of the clamping assembly at transmitting loads to the pile. Further, during insertion of the pile, such slippage can result in the pile moving upward relative to the clamping assembly housing and contacting an upper wall of this housing. Then, as further driving and/or vibratory forces are applied to the pile, the pile batters the upper wall of the housing. This can cause damage to the clamping assembly housing itself, to the assembly by which the housing is attached to the vibratory device or tensioning cable, and to the machined surfaces on the vibratory device.
Another problem with the prior art clamping assemblies is that bolts used to attach the housing thereof to a vibratory device must be installed from within the housing. This is an awkward and time consuming process and exposes the mounting bolts to the impact of the pile.
Yet another problem with prior art clamping assemblies is that, because different gripping surfaces are required for different types of piles, a different clamping assembly is required for each of the types of piles that will be driven or pulled. This is especially a problem in cases where wooden piles are being removed and replaced with more permanent piles such as concrete or steel. In this situation, the entire clamping assembly must be removed from the vibratory device between the removal of one pile and the insertion of another.
From the following discussion, it will be apparent that these and other problems with prior art clamping assemblies are solved by the present invention.